advt n disadvt of six sigma

7/29/2019 Advt n Disadvt of Six Sigma

1/8

Six Triumphs and Six Tragedies

of Six SigmaT. N. Goh

Industrial and Systems

Engineering Department,

National University of Singapore,

Singapore

ABSTRACT Six Sigma as a quality improvement framework has enjoyed an

unprecedented long period of popularity. This article brings out factors

that contribute to the uniqueness of Six Sigma, with its extensions and

derivatives such as Design for Six Sigma and Lean Six Sigma. Those features

that have brought about an impetus for quality improvement are regarded as

triumphs of Six Sigma, whereas some worrying trends in the practice of

Six Sigma are labeled as tragedies. Clearly, industry should leverage onthe strengths of Six Sigma and be careful not to become unwitting victims

of the weaknesses. A realistic and balanced view is certainly called for at this

juncture, and the advantages and pitfalls associated with Six Sigma should

be fully recognized if Six Sigma is to continue its winning streak of the past

quarter of a century.

KEYWORDS Design for Six Sigma, Lean Six Sigma, quality engineering, quality

management, Six Sigma, statistical thinking

INTRODUCTION

Some 20 years ago, at the height of popularity and controversy of the

so-called Taguchi methodsexemplified by Taguchi (1986)an article

by Pignatellio and Ramberg (1991) appeared in Quality Engineering point-

ing out the positive and negative aspects of the Taguchi version of quality

engineering and experimental design, with the euphoria in industry at that

time as a backdrop. Today, Taguchi is no longer on the lips of quality

engineers and managersat least, it is not deemed fashionable anymore

to talk about it. In fact, consultants can no longer make easy money

by repeating the NBC mantra If Japan can, why cant you? With the

recent great Toyota automobile recalls, from now on even the ToyotaMethod of production probably will have to be put on the back burner

at least for some time. This article addresses a subject that is all American,

something that has replaced Taguchi method as the most talked-about

quality improvement approach for almost two decades. This is, of course,

Six Sigma, on which there has been such an abundance of literature that

elaboration on its contents would be unnecessarysee, for example,

Harry and Schroder (1999), Hahn et al. (2000), Goh (2002), and Brady

and Allen (2006).

Address correspondence to T. N. Goh,

Industrial and Systems EngineeringDepartment, National University of

Singapore, 10 Kent Ridge Crescent,Singapore, 119260. E-mail:

[email protected]

Quality Engineering, 22:299305, 2010

Copyright# Taylor & Francis Group, LLC

ISSN: 0898-2112 print=1532-4222 online

DOI: 10.1080/08982112.2010.495102

299


2/8

Six Sigma, in the course of its development, has

generated a number of derivatives and extensions,

such as Design for Six Sigmae.g., Tennant

(2002)and Lean Six Sigmae.g., George (2002).

In this article, the term Six Sigma covers all these

variants collectively because they share basically

the same analytical foundations, with similar modes

of application. Regardless of the variant, Six Sigma

has commanded wide attention in industry and,much like the Taguchi phenomenon in the 1980s,

success stories abound in many publications; detrac-

tors inevitably also have their say from time to time;

for example, Lee (2001), Schrage (2001), Morris

(2006), and Mika (2006). However, arguments

against Six Sigma such as these are not usually

made on rigorous grounds; likewise, promoters of

Six Sigma tend to offer casual promises such as

Savings can hit $300 K per project, so a single Black

Belt can potentially bring a company $1.2 million to

the good annually (Harry and Crawford 2005).Thus, some realistic assessment of all things Six

Sigma at this juncture would not be out of place,

in view of the surge of interests in Six Sigma in indus-

try on one hand and the considerable investments

made by companies in manpower development

and external expertise on the other. Only with better

understanding of the subject could an organization

leverage on Six Sigmas strengths and overcome its

weaknesses and be able to answer this question with

confidence: To Six Sigma, or not to Six Sigma?

WHAT QUALIFIES TO BE MENTIONED

Just as Pignatellio and Ramberg (1991) effectively

used the triumphs and tragedies categorization

to highlight the notable aspects of Taguchi methods,

a similar approach is taken here with respect to Six

Sigma. Discussions of features of Six Sigma abound

in the literature, such as Hahn (2005), but presented

here will be the most important facts that an individ-

ual or company ought to know about Six Sigma.

For this reason, only six of each category are broughtup, though the lists could be readily extended.

Some explanation of these categories is in order.

What constitutes a triumph? Basically, a triumph

exists when in the field of quality engineering there

has not been a similarly meritorious approach or

methodology before; the item in question must be

able to lead to a significant impact or paradigm shift,

with results that are of practical value; that is, not just

a theoretically elegant scenario. What, on the other

hand, qualifies as a tragedy? The answer is any

feature that, if unchecked, could negate a triumph,

create misguided or misled actions, or even destroy

what originally has been useful. The selection of

six items in each category is by no means definitive

or unique and has been made largely based on the

authors personal experience in training, consulting,and research in Six Sigma over many years. Because

the relative significance of each item is a matter of

personal opinion, there is no particular order in

which the items are presented in the following

sections.

SIX SIGMA TRIUMPHS

Triumph No. 1

Use of a common, realistic metric for qualityassessment and improvement: The use of critical-to-

quality (CTQ) and defects per million opportunities

(dpmo) as performance indices is a trademark of

Six Sigma. Deliberations on the choice and definition

of CTQ would help focus on the meaningful and

avoid the inconsequential. As a yardstick for measure

of performance, dpmo allows ready comparisons of

performance such as one process versus another,

before versus after, as well as cross-process com-

parative studies. This is also associated with an

equivalent yardstick, namely, sigma level that canbe used for purposes such as benchmarking and

project target setting. It may be noted, though, that

not all outcomes are binary (defective or nonde-

fective), and in some cases even a binary classi-

fication can be arbitrary (e.g., the time it takes to

respond to a certain category of customer request).

The important point is that, for the first time, zero

defect is no longer an often-spoken-of but elusive

goal (or worse, a lip service); instead, one is sup-

posed to face the realistic challenges of non-zero

defect situations squarely. This is an important para-digm shift, with which the nebulous promise of zero

defect is abandoned, though serious efforts are made

(with effective infrastructure and tools, as detailed in

the descriptions of other triumphs later on) to inch

toward that goal. Furthermore, with Six Sigma, there

are now generic metrics for marking progress; the

defect measurements in the hands of the quality

T. N. Goh 300


3/8

practitioner transcend processes and industries of

different nature. Generally, concepts expressed in

terms ofdpmo and sigma levels can be more readily

explained and accepted by management than more

formal mathematical jargons.

Triumph No. 2

Clear assignment of roles and responsibilities inperformance improvement efforts: Another important

paradigm shift that comes with Six Sigma is ditching

of the refrain Quality is Everybodys Business. The

intent of this statement may be good and valid, but in

the real world this could be taken to imply diffused

responsibilities, especially whenever there are pro-

blems, with the assumption that everybody is equally

capable of handling quality issues. It is well known

that in many situations, Everybodys Business in

the end could degenerate into Nobodys Business.

Not so in Six Sigma; personnel with variousdegrees of training and experience are designated

clearly, and there are now individuals recognized

to know more tools than others when it comes to

performance improvement or problem solving.

Thus, there is a commonly acknowledged hierarchy

of people: ChampionsMaster Black BeltsBlack

BeltsGreen BeltsYellow Belts that have different

professional responsibilities in an organization. In

addition, the success of Six Sigma depends largely

on top management leadership rather than the pre-

vious bottom-up concepts: quality control circles,for example, may still have their place in handling

specific local problems, but they cannot be the staple

diet for fundamental organizational performance

enhancement and customer satisfaction.

Triumph No. 3

Logical alignment of statistical tools: The concept

that the whole is larger than the sum of the parts

cannot be truer when it comes to the deployment

of statistical tools in Six Sigma. Many an academichas pronounced that there is nothing new in Six

Sigma. This is true when Six Sigma methodologies

are taken apart; for example, distribution functions

describing variability have been described in detail

in many books before, process capability analysis is

a known and used concept, analysis of variance

is recognized by every student of statistics, gage

repeatability and reproducibility study is an

established procedure, design of experiments is not

a fresh concept, control charts have been applied

for decades . . . and indeed there are already plenty

of well-established college courses or on-the-job

training programs on these subjects. So, whats new?

What is new, as offered by Six Sigma, is the align-

ment and integration of statistical toolsheretofore

taught and learned in a disjointed mannerinto alogical, purposeful sequence for CTQ improvement

and business competitiveness. Specifically, the

tools are built into a DefineMeasureAnalyze

ImprovementControl (or DMAIC) framework that

suggests, for example, that a process be optimized

via statistical design of experiments in the Improve

phrase before being sustained by control chart appli-

cations in the Control phraseinstead of drawing

up a control chart for something that is not even

known to be optimal or otherwise. In fact, in pre-Six

Sigma days, the more effective the control chart, thelonger the continuation of some nonoptimized pro-

cess. In other words, Six Sigma makes statistics work

harder (by seeking the optimal) and smarter (by

focusing on the best) in the hands of nonstatisticians.

Triumph No. 4

Recognition of the time effects on processes: Talk-

ing about the use of statistics by nonstatisticians

in the past, for understandable reasons, practically

only time-invariant models are used by the rank-and-file. Six Sigma does not provide the full answer to the

consequences of time-dependent natural changes,

but it does bring up the concept of short-term

versus long-term variation; that is, the 1.5 sigma

shift in the assessment of dpmo and sigma levels.

Although the rationale for such a shift is an unre-

solved issue (see, for example, ASQ Discussion

Boards [2005]), the fact remains that Six Sigma is

the only quality improvement approach that promi-

nently recognizes and fully takes into account what

any experienced quality practitioner must havefaced: the relentless realization of the second law

of thermodynamics, meaning Things left to them-

selves will deteriorate. No procedures, formulated

by textbooks or otherwise, prior to the advent of

Six Sigma required practitioners to express this real

and important phenomenon explicitly up front.

Regardless of the exact nature of a process one

301 Six Triumphs and Six Tragedies of Six Sigma


4/8

is handling, this is an insightful defensive and

preemptive move.

Triumph No. 5

Unprecedented synergy with modern information

technology: Six Sigma attained its popularity among

practitioners because it arrived at the right time.

Should Six Sigma have appeared on the scene, say,20 years earlier than the mid-1980s, it would not take

off because it is statistics basedthe shear amount of

data crunching would mean that only dedicated

personnel hired to crank big and noisy mechanical

calculators would want to have anything to do with

it. Many have lamented the nonuse of statistics in

industry, for example, Penzias (1989), but few have

admitted the real and perceived obstacles, namely,

the efforts it would take to gather, store, transform,

and analyze data in industrial settings.

By the 1990s, with the appearance and swiftprevalence of both hardware and software brought

about by the age of information technology, that is,

personal computers, notebook computers, with

user-friendly versions of the likes of MINITAB and

JMP, application of Six Sigma no longer demands

deep knowledge of statistical theory or superior data

processing capabilities. The credit may not entirely

lie in the contents of DMAIC, but winning over

hesitant onlookers and converting industry people

into aficionados of statistical tools is an undeniable

triumph of Six Sigma.

Triumph No. 6

Capabilities to grow for larger roles for business

competitiveness: Unlike many other quality tools or

certification systems that remain essentially the same

throughout their useful life, Six Sigma is organic. Six

Sigma as applied in industry today can be a far cry

from the Six Sigma of the 1980s. Through the years,

Six Sigma has been augmented, extended, and

transformed into even more comprehensive frame-works that are applicable all the way from design

to manufacture (of products) or implementation (of

service systems).

Design for Six Sigma and Lean Six Sigma, in a var-

iety of roadmaps in different organizations, are major

examples of the upshot of the classic Six Sigma

formula from Motorola. The former reflects the belief

that Prevention is better than cure, and the latter

recognizes that waste elimination should go hand

in hand with variation reduction. There is no appar-

ent limit to what Six Sigma might be morphed into in

the years to come: mass customization, for example

(Piller and Tseng 2010), is one possible direction

for development. In recent years, serious attempts

to introduce Six Sigma into service sectorsgovern-

ment, education, health care, transportation, tourism,etc.actually reflect the vitality of Six Sigma and

constitute a veritable triumph over any narrowly

defined and applied procedures for quality.

SIX SIGMA TRAGEDIES

Not all things associated with Six Sigma are flaw-

less, however. Some of the unsatisfactory aspects of

Six Sigma are not inherent in Six Sigma itself but in

the way in which Six Sigma is learned or deployed.

Left unchecked, such weaknesses could lead to theundoing of Six Sigma in the long run. Opinions could

differ, but the accounts given below are based on

what has been observed in industry.

Tragedy No. 1

The belief that Six Sigma (as typical Black Belts

know it) is universally applicable: This is related to

the growing extension of Six Sigma applications,

especially to nonmanufacturing systems. Unfortu-

nately, this is where the Achilles heel of the commonSix Sigma body of knowledge exhibits itselfeven

though the training of Six Sigma workers has been a

frequent subject of discussion; see Hoerl (2001), for

example. Many run-of-the-mill Black Belts are ignor-

ant of, for example, queuing theory, methods for

discrete observations, as well as the nature of ordinal

scales or correlated observations commonly found in

service systems. Many of them would take on service

quality projects with the idea that they have already

been well prepared by the standard Black Belt

training program.In principle, it is commendable for a quality pro-

fessional to try to push the boundaries of Six Sigma

applications. However, Black Belts using conven-

tional Six Sigma procedures on service systems could

end up with results that could not stand up to serious

scrutiny of a good statistician. The problem could

be compounded in some situations where

T. N. Goh 302


5/8

recommendations cannot be tested or demonstrated

because the system in question has already changed

in characteristics or boundaries over the project

duration. The tragedy is doubled if the Black Belts

are not even aware of their own inadequacy or

limitations and, instead, brandish to management

or customers the outcomes of half-baked studies.

Tragedy No. 2

Obsession with personal attainments: As in many

other situations, the means could gradually and

unwittingly become the end. Witness the myriad

of overprized (or, interestingly in some cases,

discounted) commercial Black Belt or Green Belt

training programs that promise certification at the

end. It seems forgotten that customers benefits,

and ultimately an organizations business interests,

were the very motivation for Six Sigma originally.

This is where some CTQ ought to be defined: is SixSigma meant to benefit an organizations customers

or a certification project owner?

Because Six Sigma calls for a hierarchy of profes-

sionals with a differentiation in levels of expertise

and responsibilities, designation by different colors

of belts is useful. However, most advertisements

today for Six Sigma training and many potential

takers seem to treat certification to a belt of a certain

color to be the sole objective; the brutal fact is that

classes are nowadays offered with individuals

improved resumes as the unabashed motivation,rather than any customers improved satisfaction or

any organizations improved bottom line. A practice

has already been observed that presents BB or

MBB in a resume as it were a professional degree,

rather than a role within Six Sigma implementation.

Tragedy No. 3

The idea that professional statisticians are no

longer needed: The main feature that contributes to

the triumphs of Six Sigma could become an inhibitorof further successes. Many Six Sigma workers, parti-

cularly freshly minted Black Belts, tend to have the

idea, albeit an implicit one, that the tools entailed

in DMAIC are both necessary and sufficient for prob-

lem solving in the real world. (Tragedy No. 1 thus

comes to mind again). The certification process, if

anything, helps foster this misconception because it

implies that an individual is now fit to handle Six

Sigma implementation; in reality, all it means is that

the person has satisfied certain requirements pre-

scribed by anything from an established organization

such as ASQ to a fee-grabbing consulting outfit with

unknown track record.

Admittedly, some enlightened trainers and their

learners are aware of the ocean of knowledge and

tools left untouched during the standard Six Sigmatraining: a well-designed training program would

use the Pareto principle to emphasize to the trainees

that what is covered, the vital 20%, is actually not

always needed, whereas the rest, 80% of other tools

not in the DMAIC syllabus, are not really all trivial

and occasionally have to be called forfor that, help

from professional statisticians would certainly be

needed. For a fuller discussion, see, for example,

Hahn and Hoerl (1998).

Tragedy No. 4

Irresponsible hype of Six Sigma: Many, especially

managers, are attracted by easy benefits casually pro-

mised by Six Sigma promoters, many of whom now-

adays could be entirely commercially motivated. For

example, it remains to be proven whether seductive

statements such as this are scientifically supported:

As much as $175,000=project and $1 million=yr=

Black Belt (Harry 1998; interestingly, one may note

the inconsistency between this promise and the

statement quoted in the Introduction section ofthis article). It is real, though, that exorbitant

amounts tend to be quoted by many commercial

training-cum-certification offerings. Other motiva-

tors include descriptions, accompanied by data

and graphs, of enviable rises in stock prices that only

Six Sigma companies would enjoy, though the fact

was that during the early 1990s, there was a general

rise in stock prices in the United States, and practi-

cally all prices dipped toward the end of 2008,

Six Sigma or no Six Sigma! There actually was a

formal study on this subject some time ago (Gohet al. 2003).

Because the likes of General Electric are invariably

held up as models for Six Sigma implementation, for

example, Snee and Hoerl (2003), the practice begs

the question as to whether only organizations with

the scale and operations of General Electric would

benefit from Six Sigma deployment. The upshot is



6/8

likely to be either (a) smaller organizations believe

that Six Sigma is not appropriate for them, therefore

ignoring it; or (b) such organizations are disillu-

sioned when the fancied extraordinary profits turned

out to be too good to be true and do not materia-

lizeafter hefty fees have been paid out and no one

is answerable for the failure of Six Sigma. If this is

not a tragedy, one wonders what is.

Tragedy No. 5

A bigoted In Data We Trust mentality: Precisely

because Six Sigma is data driven, sometimes a prac-

titioner could go overboard with statistical evi-

dence. Thus, arguments could be advanced in

favor of a course of action on the strength of some

p-value generated by some computer software,

rather than considered opinions based on the experi-

ence or insights of business leaders. This is parti-

cularly seen in projects presented for certificationpurposes: one could get the impression that the

world is ruled by outputs from MINITAB (or such

like), because once some p-value falls within a cer-

tain range and the residual checks look passable,

all would seem to live happily ever after. This is

not to say, of course, that different attitudes cannot

be found; a good Six Sigma training program would

produce professionals who are masters, rather than

slaves, of statistical tools and software packages.

In fact, the slave mentality in Six Sigma is exem-

plified by a practitioners confidence and ability inhandling merely quantitative information. Some

would make a mountain out of a molehill, using data

of dubious quality or data from some poorly con-

structed or responded survey. Not a few would be

at a loss when encountered with a CTQ that is obvi-

ously non-numeric. A quote would suffice to

describe the syndrome and its consequence: To

many it will always seem better to have measurable

progress toward the wrong goals than unmeasurable

progress toward the right ones (Galbraith 1978).

Apparently the tragedy is not confined to the worldof economists.

Tragedy No. 6

Ignorance or neglect of what is important beyond

DMAIC: Six Sigma as commonly practiced is

technology-blind and human-ignorant. In particular,

those wearing Belts of whatever color in Six Sigma

are expected to conform to the DMAIC straitjacket.

Quick results and tangible savings are sometimes

engineered to reflect the success of a project

especially by those associated with the unguaranteed

profit promises, as pointed out previously. This is not

necessarily consistent with customer satisfaction or

business competitiveness, because suboptimization

and short-term benefits could be mistaken as funda-mental improvements. Even adherence to, say, the

3.4 dpmo benchmark is not always logical; it could

actually go against customer satisfaction, as pointed

out elsewhere (Conti et al. 2003). A parable on sub-

optimization can be drawn from a scene in the movie

Titanic, in which one could certainly applaud the

exquisite music performed with seamless teamwork

by the quartet, oblivious of the fact that the ship

was slowly sinking! (In the same vein, one could

ask: would it make sense to throw in Six Sigma man-

power to improve the productivity of a mechanicaltypewriter assembly line?)

There is one further point that is no less important.

One expectation of Six Sigma is the development of

Black Belts into business leaders of the future. Leav-

ing aside the rigidity of DMAIC (during the

certification-based training anyway), it is clear that

nothing in Six Sigma prepares a Black Belt for tech-

nology changes or breakthroughs, technology substi-

tution, lifestyle evolution, or cultural differences.

Furthermore, human attributes that relate to suc-

cesses are hardly ingredients found in DMAIC:imagination, vision, passion, insight, judgment, crea-

tivity, curiosity, perseverance, just to name a few

though this is not to imply that none of these has

been seen in actual Six Sigma endeavors. The spirit

of innovation, synergy, breakthrough, and entrepre-

neurship, for example, could prove to be the prime

mover of an organization, not the behavior of many

a Six Sigma certification seeker. So the point is, it

would be tragic indeed if carefully chosen and

nurtured Black Blacks fail to realize their potential

precisely because of what is lacking in Six Sigmaitself.

CONCLUDING REMARKS

In the final analysis, Six Sigma offers a quality

improvement and business excellence roadmap

inspired by statistical thinking and guided by

T. N. Goh 304


7/8

data-driven techniques. In this respect, useful

insights can be gained from, for example, Hoerl

and Snee (2002). The observations highlighted in

the previous sections arose, as explained before,

from the authors experience in organizations

ranging from ones with a handful of employees to

one of General Electrics large companies, personally

interacting with nationals of about a dozen countries

over the years. The discussions here are motivatedby the fact that there are still companies today trying

to decide, among other things, whether it is wise or

safe to embrace Six Sigma, so to speak, after being

exposed to various forms of publicity on the subject.

This article is basically a two-pronged promotion

of Six Sigma, namely, a call for reinforcement of its

merits or triumphs and sounding of caution where

tragedies could happen. Promoters of Six Sigma

may well highlight the inherent Six Sigma triumphs

to the uninitiated, but they owe the quality pro-

fession a responsibility to minimize the chances oftragedies. In particular, they should avoid the greed

and fear approach in securing the next Six Sigma

buyer (yes, for want of a better word); this author,

for one, considers arguments such as the $XXXsav-

ings per project inducement and the 99% not good

enough threat as used by some Six Sigma peddlers

cheap, nonprofessional, and an intellectual insult to

business leaders. In fact, Six Sigma does not need

to depend on hyperbole to gain acceptance; with

responsible professionals conscious efforts to avert

potential tragedies, it has all the ingredients to con-tinue to be triumphant for many years to come.

ABOUT THE AUTHOR

T. N. Goh holds a B.E. from the University of

Saskatchewan and a Ph.D. from the University of

WisconsinMadison. A Fellow of ASQ and Aca-

demician of the International Academy for Quality

(IAQ), he is also a former Director of the Office of

Quality Management and former Dean of Engineer-

ing at the National University of Singapore. He is acoauthor of the book Six Sigma: Advanced Techni-

ques for Black Belts and Master Black Belts (Wiley,

2006) which won the inaugural Masing Book Prize

of the IAQ. Currently he serves on the editorial

boards of ten international technical journals.

REFERENCES

ASQ Discussion Boards. (2005). Various contributions. Available at:

http://www.asq.org/discussionBoards/thread.jspa?threadID=1517&

forumID=18

Brady, J. E., Allen, T. T. (2006). Six Sigma literature: A review and agenda

for future research. Quality and Reliability Engineering International,

22(3):335367.

Conti, T., Kondo, Y., Watson, G. H., Eds. (2003). Quality into the

Twenty-First Century. Milwaukee, WI: ASQ Quality Press.

Galbraith, J. K. (1978). The New Industrial State, 3rd ed. Boston:

Houghton Mifflin.

George, M. L. (2002). Lean Six Sigma: Combining Six Sigma Quality with

Lean Production Speed. Blacklick, OH: McGraw-Hill.

Goh, T. N. (2002). A strategic assessment of Six Sigma. Quality and

Reliability Engineering International, 18(5):403410.

Goh, T. N., Low, P. C., Tsui, K., Xie, M. (2003). Impact of Six Sigma

implementation on stock price performance. Total Quality and

Business Excellence, 14(7):753763.

Hahn, G. J. (2005). Six Sigma: 20 Key lessons learned: Experience shows

what works and does not work. Quality and Reliability EngineeringInternational, 21(3):225233.

Hahn, G. J., Doganaksoy, N., Hoerl, R. W. (2000). The evolution of Six

Sigma. Quality Engineering, 12(3):317326.

Hahn, G. J., Hoerl, R. W. (1998). Key challenges for statisticians in busi-

ness and industry. Technometrics, 40(3):195200.

Harry, M. J. (1998). Six Sigma: A breakthrough strategy for profitability.

Quality Progress, 31(5):6064.

Harry, M. J., Crawford, D. (2005). Six SigmaThe next generation.

Machine Design, February.

Harry, M. J., Schroeder, R. (1999). Six Sigma: The Breakthrough Manage-

ment Strategy Revolutionizing the Worlds Top Corporations.

New York: Doubleday.

Hoerl, R. W. (2001). Six Sigma Black Belts: What do they need to know?

(with discussion). Journal of Quality Technology, 33(4):391435.

Hoerl, R. W., Snee, R. D. (2002). Statistical Thinking: Improving BusinessPerformance. Pacific Grove, CA: Duxbury Press.

Lee, C. (2001). Why you can safely ignore Six Sigma. Fortune, January.

Mika, G. (2006). Six Sigma isnt lean. Manufacturing Engineering, July.

Morris, B. (2006). New rule: Look out, not in. Fortune, July.

Penzias, A. (1989). Teaching statistics to engineers [Editorial]. Science,

244(4908):1025.

Pignatiello, J. J., Ramberg, J. S. (1991). Top ten triumphs and tragedies of

Genichi Taguchi. Quality Engineering, 4(2):211225.

Piller, F. T., Tseng, M. M., Eds. (2010). Handbook of Research in Mass

Customization and Personalization. Singapore: World Scientific.

Schrage, M. (2001). Make no mistake? Fortune, December.

Snee, R. D., Hoerl, R. W. (2003). Leading Six Sigma: A Step-by-Step Guide

Based on Experience with GE and Other Six Sigma Companies. Upper

Saddle River, NJ: FT-Prentice Hall.

Taguchi, G. (1986). Introduction to Quality Engineering. Tokyo: Asian

Productivity Organization.

Tennant, G. (2002). Design For Six Sigma: Launching New Products and

Services without Failure. Hampshire, UK: Gower.



8/8

Copyright of Quality Engineering is the property of Taylor & Francis Ltd and its content may not be copied or

emailed to multiple sites or posted to a listserv without the copyright holder's express written permission.

However, users may print, download, or email articles for individual use.

advt n disadvt of six sigma

Documents